1. Field of the Invention
The invention relates to a Zener diode.
2. Description of Related Art
Japanese Patent Application Publication No. 7-321347 (JP 7-321347 A) describes a Zener diode. An n-type impurity concentration of an n region that constitutes a pn junction of a Zener diode is low, an avalanche breakdown mainly occurs at the time of a breakdown of the Zener diode. In this case, the avalanche breakdown has a positive temperature coefficient, so the characteristic of the Zener diode changes depending on temperature. In contrast, in the Zener diode described in JP 7-321347 A, a pn junction is formed of a high-concentration p region and a high-concentration n region. Thus, both an avalanche breakdown and a Zener breakdown occur in a balanced manner at the time of a breakdown of the Zener diode. A Zener breakdown has a temperature coefficient opposite to an avalanche breakdown. Therefore, by causing both an avalanche breakdown and a Zener breakdown to occur, it is possible to improve the temperature characteristic of the Zener diode.